The present invention relates to compositions and gating system components for metal casting and processes for use in casting of molten metals in a foundry setting. More particularly, the invention relates to such compositions and articles which are self sintering when brought in contact with molten metals or otherwise heated.
Heretofore, various components of gating systems used in metal foundry molds have been formed out of extruded and subsequently high temperature fired ceramic materials to produce a system of sleeves, cups, funnels, downsprues and runners for forming a gating system for conveying of molten metals which are introduced into a mold, which itself is often formed of a sand-based material. Risers are also connected to the mold to ensure adequate quantity of molten metal to fill the mold as it contracts upon cooling. Due to the fact that the ceramic sleeves used are formed from fired ceramics, they are dense and heavy and must be cut with a diamond blade wet saw or a special cut-off saw in order to customize the length and shape thereof to be adapted to a particular casting. See, for example, U.S. Pat. Nos. 4,177,066 and 4,469,161. Another disadvantage of such materials is that they tend to act as a heat sink, thus tending to cool the molten metal to some degree. Also, since the parts are formed by extrusion, only simple tubular shapes, without special contours or variations in diameter, are obtainable, unless such parts are machined.
In other foundry applications a fibrous ceramic material may be used, for example, as a sleeve, cup or funnel. Such materials are generally held together with a resin binder, for example, a phenolic resin which will, at molten metal temperatures, be burned away, thereby resulting in disintegration of the fibrous ceramic shape. A need has existed for tubular ceramic materials which would be economical, easy to shape, for example, by cutting by means of a hand tool but yet which would withstand the elevated temperatures necessary to allow flow of molten metal through a gating system into a mold cavity.